Daylight control circuit



Jan. 27, 1970 E, McKEE 3,492,529

DAYLIGHT CONTROL CIRCUIT Filed Aug. 1, 1968 VOLI'A 6E M 52 14/14 POM?! GOA/7726M 46 4 FROM f/MER 47 I 20 JVVV 1 000? Mc zfee INVENTOR.

United States Patent Ofl ice 3,492,529 Patented Jan. 27, 1970 Texas Filed Aug. 1, 1968, Ser. No. 749,355 Int. Cl. H05b 37/02, 39/04, 41/36 U.S. Cl. 315--149 3 Claims ABSTRACT OF THE DISCLOSURE An improvement in a daylight control circuit for turning off the power to a lamp flasher during daylight hours in which the control circuit is unaffected by the light produced from the lamp. A daylight control circuit including first and second switching means connected in series with a voltage source connected to the second switching means, a first resistor connected to said first switching means and to the voltage source for actuating the first switching means, the second switching means connected to and actuated by a timer, a light sensitive resistor one side of which is connected between the first resistor and the voltage source, a third switching means connected to the voltage source in parallel with the first and second switching means and controlled by the series circuit of the first and second switching means at a point connected to the output to the lamp, and a diode connected between the third switching means and the first switching means for actuating the first switching means independently o the light sensitive resistor.

BACKGROUND OF THE INVENTION The present invention relates to an improvement in a daylight control circuit for a lamp flasher controlled by a timer in which the daylight control circuit is unaffected by the light produced from the lamp.

In general, lamp control circuits utilizing a light sensitive resistor for turning off the light control circuit to a lamp flasher thereby conserving power during the daylight hours is old. However, in many of the prior lamp flashers the light from the lamp illuminated the light sensitive resistor causing the resistor inadvertently to shut off the power to the lamp thereby adversely affecting the desired operation of the lamp flasher.

The present invention overcomes this problem by insuring that the light sensitive resistor will sense daylight and control the daylight control circuit, but is unaffected by the light produced from the lamp, without regard to the length of time the lamp is illuminated.

SUMMARY The present invention is directed to an improvement in a daylight control circuit having a light sensitive resistor which is unaffected by the light produced from a lamp flasher controlled by the daylight circuit.

The present invention is further directed to a daylight control circuit in which the timer, which actuates the lamp flasher, actuates an auxiliary circuit for maintaining power to the lamp while the timers signal is actuated to bypass the effect of a light sensitive resistor which may be subjected to light flashes from the lamp, but in which the light sensitive resistor will control the power to the lamp whenever the timer signal is off.

BRIEF DESCRIPTION OF THE DRAWING The drawing is an electrical schematic illustrating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, the daylight control circuit is generally indicated by the numeral 10 and includes an input 12 for receiving lamp actuating signals from a conventional timer (not shown) and an input terminal 14 providing a signal to actuate the power to a flasher lamp, and a voltage supply terminal 16.

A conventional light sensitive resistor 18 is provided which has a low resistance when exposed to the light and a high resistance when unexposed to light, the high resistance being large compared to that of the resistance of resistors 20 and 22.

Assuming that the resistor 18 is in darkness, its resistance is large and a current will flow from voltage supply terminals 16 through resistors 22 and 20 to the base 24 of switching means or transistor 30 switching the transistor 30 into an on or conducting position. Similarly, a current will flow through resistors 32, 34 and 36 to the base 38 of switching means or transistor 42 turning transistor 42 on.

When a timing signal is received at input 12 from the timer (not shown) and applied through resistor 44 to the base 46 of switching means or transistor 50, transistor 50 is turned on and is in a conducting state. Since both transistors 30 and 50 are conducting, the voltage on the colleetor 48 of transistor 50 will be zero and thus a voltage of zero volts is present at junction 52. A potential of zero volts at junction 52 is the signal to output 14 required to actuate the supply power to the flasher lamp (not shown).

When the voltage at point 52 goes to zero, transistor 42 will stop conducting, and thus the voltage on its collector 40 will rise. The increase in voltage on collector 40 will provide a current flow through resistor 54, diode 56 and to the base 24 of transistor 30 thus keeping transistor 30 in a conducting state even though the light sensitive resistor 18 may be illuminated by a light from the flasher lamp. Thus even though the resistance of resistor 18 may be low thereby stopping the flow of current through resistor 20 to the base of transistor 30 the transistor 30 will remain on. Thus, the transistor 30 cannot cease conducting as long as the voltage at point 52 remains at zero thereby providing a current flow through resistor 54 and diode 56. The time that the voltage remains zero at junction 52, is the duration of the timer pulse and thus so long as a timing pulse is being applied, the light sensitive resistor 18 cannot cause the power to the lamp to be interrupted even though it may be illuminated by the light from the flasher lamp.

However, if the light sensitive resistor 18 is exposed to daylight during the time that no timer signal is applied to the input 12, transistor 30 will not be in a conducting state because the now low resistance of resistor 18 prevents a current flow through resistors 22 and 20, and since transistor 42 is now conducting the flow of current through diode 56 is limited. Therefore, if the transistor 30 is not in a conducting state at the time a timing signal is received from the timer at the input 12, the voltage at point 52 cannot go to zero, which means that an on signal will not be applied to the lamp power control through the output 14 until the light sensitive resistor 18 is again actuated by darkness.

In operation, so long as the light sensitive resistor 18 is subjected to daylight, the transistor 30 is nonconducting and no power will be applied to the lamp. When it becomes dark, the resistance of resistor 18 increases and the current will flow through the base emitter junction of transistor 30 which causes transistor 30 to turn on. Then, when a signal is received at the input 12 from the timer,

transistor 50 is turned on and a voltage of zero volts is applied to junction 52 which is the required signal to the lamp power control to supply power to the lamp at output 14. With the voltage at junction 52 at zero, transistor 42 will cease conducting and current will flow through diode 56 to keep transistor 30 on even in the event that light from the lamp which is now being actuated turns off the light sensitive resistor 18. Thus transistor 30 cannot cease conducting as long as the voltage at junction 52 remains at zero, which is for the duration of the timer pulse. And, of course, when the timer pulse ceases the light from the lamp also ceases and the light sensitive resistor 18 will again have a large resistance thereby continuing the actuation of transistor 30 in preparation for the next timer pulse.

The present invention, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment is given for the purpose of disclosure, numerous changes in the details of construction and arrangement of parts can be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a daylight control circuit having an output connected to the lamp power control and an input connected to a timer for periodically actuating said light, the improvement of a circuit which is unaffected by the light produced from the lamp comprising,

first and second switching means connected in series to a voltage source connected to said second means,

a first resistor connected to said first switching means and to the voltage source for actuating said first switching means,

said second means connected to and actuated by said timer,

a light sensitive resistor having a low resistance when exposed to light and a high resistance when unexposed to light, one side of said resistor connected between said first resistor and said voltage source, the other side to ground,

a third switching means connected to said voltage source and in parallel with the first and second switch ing means, said third means actuated by a connection to the series circuit of the first and second means at a point between the first and second means and the voltage source,

said output to the lamp power control being connected to said point,

a one way current device, one side connected between said third means and said voltage source and the other side connected to said first means for actuating said first means when the third means is deactuated by a signal from the timer actuating the light.

2. In a daylight control circuit having an output connected to the lamp power control and an input connected to a timer for periodically receiving signals actuating said light, the improvement of a circuit which is unaffected by the light produced from the lgmp comprising,

a light sensitive resistor having a low resistance when exposed to light and a high resistance when unexposed to light, said resistor connected between a voltage source and ground,

a first transistor having a base, emitter and collector, the base of which is connected between the voltage source and the light resistor,

a second transistor having a base, emitter and collector,

the base being connected to said timer, and the emitter of the second transistor being connected to the collector of the first transistor,

a third transistor having a base, emitter and collector, the base being connected to the output connected to the lamp power control which is connected to the collector of the second transistor, the collector circuit of the third transistor being connected to said voltage source, and

a diode connected between the collector of the third transistor and the base of the first transistor.

3. In a daylight control circuit having an output connected to the lamp power control and an input connected to a timer for periodically actuating said light, the improvement of a control circuit which is unafiected by the light produced from the lamp comprising,

a light sensitive resistor having a low resistance when exposed to light and a high resistance when unexposed to light, said light sensitive resistor connected a voltage source and ground,

a first transistor having a base, emitter and collector,

the emitter of which is connected to ground,

a second resistor connected between the base of the first transistor and to a point between the voltage source and said light sensitive resistor,

a second transistor having a base, emitter and collector, the emitter being connected to the collector of the first transistor, the base being connected to the timer, and the collector being connected to the output to the lamp power control,

a third transistor having a base, emitter and collector, the emitter being connected to ground, the collector being connected to the voltage source, and the base being connected to the collector of the second transistor, and

a diode being connected between the collector of the third transistor and the base of the first transistor.

References Cited UNITED STATES PATENTS 2,891,195 6/1959 Smyth 315159 2,973,456 2/1961 Smyth 3l5l59 3,319,116 5/1967 Schick 315-83 3,377,507 4/1968 Riebs 315-159 JOHN W. HUCKERT, Primary Examiner B. ESTRIN, Assistant Examiner US Cl- X-R, 3151 58, 15,9 

